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Old 04-07-2006, 09:40 AM
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Join Date: Apr 2006
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Broken Glow Plugs - One after another

1978 240D

I'm just getting into this so forgive my ignorance. These forums have been a great source so far.

A few days ago I went to start her up and the GP light never came. I figured the bulb might just be out and tried to start anyway. No-Go. I tested the glow plugs and found that #1 was an open circuit and the others were not. (I need a new multimeter so I can get an actual ohm reading)

So... I replaced the first glow plug, and when I turned on the ignition, the GP light came on. I tried to start the engine but no go. I thought it just might take another try becasue it was sitting for 2 days but when I tried to give it another go, the GP light didn't come on and the #1 GP is an open circuit again.

(Sorry for the long story)

Any advice on what to check next would be greatly appreciated.

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Old 04-07-2006, 10:08 AM
Join Date: Mar 1999
Location: Tucker, Ga USA
Posts: 12,153
That is a series system..any glow plug that is OPEN circuit will kill the complete circuit.

IF the same plug keeps failing then normally the plug just down-stream is SHORTED causing that plug to receive the complete current flow!

YOU should replace the complete set of glow plugs & ream out the holes...!

MAKE sure NOT to over tighten the plugs as they are fragile & require very little torque as they have taper seats. 20-25Nm
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Old 04-07-2006, 10:08 AM
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Join Date: Dec 2004
Location: Albany, OR
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You might try checking the fusable link and the relay. Sounds like something it shorting and blowing out the GP. Check for checking the system. The relay and fusable link should be on the drivers side wheel well in the engine compartment. Thats for a w123 anyway.
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Old 04-07-2006, 10:11 AM
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Join Date: Apr 2002
Location: NW WA
Posts: 6,282
1) What brand of GPs are you buying?
2) I would consider switching to the new (pencil) type fast GPs, much better and more efficient.

1985 Euro 300TD 5 spd 220K
1985 Euro 240D 5 spd 130K
1979 240D 5 spd, 40K on engine rebuild
1994 Dodge/Cummins, 5 spd, 121K
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Old 04-07-2006, 06:35 PM
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Join Date: Apr 2006
Posts: 2
Thanks for all of your help

There was a short in the the #2 GP and after I took them out and cleaned them everything worked just fine. I would imagine that this is indicative of some other troubles but I'll start with an oil change and take it from there.

Thanks for all of your help!
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